Severe accident risk reduction by containment leakage testing during operation

Two years ago the containment leakage testing requirements have been modified in Belgium. Type A tests will be performed every 10 years, but the integrity of the containment will be verified at least every year by a global low pressure leakage test performed during reactor operation. This test has the capability to detect leaks that correspond to a hole of 0.7 cm in diameter or more. To achieve this sensitivity it is necessary to choose the instrumentation carefully and to follow a good procedure. Because the containment is an important factor in mitigating the consequences of a severe accident, it is necessary not only to assess its integrity after the accident has taken place, but also to ensure that it is leaktight before. Containment leakage tests performed during reactor operation have this capability. They are therefore an important step in any severe accident risk reduction scheme, because the probability of preexisting openings, as documented up to now in the literature, is relatively high